摻雜二氧化矽之液晶電容器特性研究

Abstract

本論文旨在利用二氧化矽奈米粒子摻雜於液晶中，製作出具有記憶效果之可變液晶電容器，此電容器不需要外加電壓即能維持在一定值，藉此降低系統使用上之耗能，此可變電容可應用於提高能源採擷器之擷取效率。能源採擷器即為將周圍環境的外界能量擷取並轉換成電能之設備，為能即時與外界的隨機振動匹配，可利用此可變電容調整其共振頻率以提高擷取效率，進而達到最大能源之輸出。 在本研究中，吾人之主要研究著重於施加不同電壓與頻率對於正型液晶電容器特性之影響，藉由介電頻譜術分析其電容可調特性以及損耗特性。 最後，吾人將正型液晶材料換成雙頻液晶，以達到電容值可電壓切換之目的，並針對切換後的特性，進行一系列與正型液晶電容器相同的討論與分析。

This work presents the bistable and tunable capacitors based on silica-doped liquid crystal devices. The driving power for bistable capacitors is applied only when the capacitance changes. It has attracted our interest due to its low power consumption particularly for the power harvesting micro-devices, which convert mechanical energy into electricity. In order to improve the power harvesting efficiency, a tunable capacitor is needed for adjusting the resonance frequency of power harvesting micro-devices to match the frequency of the external vibration in real time. The influences of driving frequency and voltage on the bistability, dielectric loss and tuning ratio of silica-doped liquid crystal (E7) capacitors were studied by dielectric spectroscopy in this work. The dual frequency liquid crystal was finally applied in the silica-doped liquid crystal capacitors to obtain switchable capacitance from the memory state.